1. Field of the Invention
The present invention relates to a magnetic transducer utilizing unidirectional anisotropy and to a magnetic recording device for reading and writing information using said magnetic transducer.
2. Description of the Related Art
Unidirectional anisotropic phenomenon has been well known. This phenomenon takes place as a result of interaction when a ferromagnetic body contacts an antiferromagnetic body caused by bonding action of exchanging magnetic momentums in the boundary surface between them both. It is disclosed, for example, in Japanese Patent Application Laid-Open No. 54-10997 (1979) that exchange coupling between a ferromagnetic Ni--Fe alloy film and an antiferromagnetic Fe--Mn alloy film causes unidirectional an isotropy and consequently the B-H loop of the Ni--Fe alloy thin film is shifted from the origin. Further, as to an antiferromagnetic material showing unidirectional an isotropy other than the Fe--Mn alloy, a gamma-phase Mn alloy is disclosed in U.S. Pat. No. 4,103,315. In the patent, materials such as NiO, Fe.sub.2 O.sub.3, Ni--Mn are disclosed as other antiferromagnetic materials.
Furthermore, as to an antiferromagnetic body used for a magnetic-resistance sensor, a Mn alloy having crystal structure of face-centered cubic lattice is disclosed in Japanese Patent Application Laid-Open No. 6-76247 (1994). Particularly, alloys of Ni--Mn, Ir--Mn, Pd--Mn, Pt--Mn, Rh--Mn and alloys added with a specified element are described. The conventional materials showing unidirectional an isotropy described above are alloys of gamma phase and face-centered cubic lattice except oxide metals.
According to the conventional technology, a magnetic transducer constructed from an antiferromagnetic Fe--Mn film showing unidirectional an isotropy and a ferromagnetic Ni--Fe film has a lot of difficulties in practical use since the antiferromagnetic Fe--Mn film has an extremely low corrosion resistivity. Further, when a Fe--Mn--Cr film, which is obtained by adding Cr to a Fe--Mn alloy, is used, there is a problem in that the thermal temperature is decreased since the Neel temperature of the antiferromagnetic film is lowered with Cr.
Although the oxide metal antiferromagnetic film, such as NiO film, has a thermal resistivity of approximately 200.degree. C. and a good corrosion resistivity, there is a problem in using a magnetic transducer since the oxide metal is small in electric conductivity. The Ni--Mn film also has a problem in manufacturing since it requires a long time thermal treatment to obtain unidirectional an isotropy. As described above, the conventional magnetic transducers have disadvantages in corrosion resistivity, electric conductivity, thermal resistivity, productivity, and so on.